I don't use much social media and have things set up to block most ads. So maybe I just don't get how bad it is out there. But in my experience with Youtube I've thought it generally does a decent job at recommending me videos based on what I've watched and who I'm subbed to. For example, if I stumble across some documentary about an aircraft accident, I'm not upset when it starts recommending me other similar videos from that channel or videos from other channels and their similar documentaries. I've found good videos I'd never have seen that way.

It can get frustrating if you accidentally end up watching a video about something you normally don't want to see, but the newer recommendations seem to fade away after a few days of not watching them. And I can certainly see how such a system can be gamed in nefarious ways. I never liked when I saw Reddit sub recommendations, but I mostly thought that was because their system didn't recommend me things I had any interest in.